|The following is based on Fallout Tactics and some details might contradict canon.|
Freeport is a location in Fallout Tactics, which can be reached from Bunker Alpha. Before the war, it was a moderately sized city in the state of llinois. By 2197, the town had become a rather large raider den, housing limited supplies of fossil fuels and a large alcohol distillery.
Cypher, a raider who was also working as a Brotherhood informant, revealed where Charon was kept. A squad of Brotherhood initiates who had previously freed Brahmin Wood of raiders managed to rescue Charon and kill many unsuspecting raiders, including their leader O'Reilly, in the process. Another prisoner, Ripley, from Great Bend, was also saved.
The mission in Freeport is a stealth mission. You need to ensure that Charon is unharmed, then kill as many raiders as possible and help Charon escape.
You don't actually have to talk to the informant to complete the mission.
Freeport appears only in Fallout Tactics.